Final answer:
The amount of force produced by a muscle depends on the number of myofibers receiving an action potential. Increasing the frequency of action potentials also increases force. Muscle contraction is determined by the sliding filament model.
Step-by-step explanation:
The relationship between the electrical activity in muscles (EMG) and the amount of force produced by the muscle is determined by the number of myofibers within the muscle that receive an action potential from the neuron that controls that fiber.
When fewer myofibers are stimulated, as in the case of picking up a pencil, less force is produced. When all myofibers are stimulated, as in the case of picking up a heavy object like a piano, maximum force is produced.
Increasing the frequency of action potentials can also increase force.
The primary variable determining force production in muscles is the number of myofibers that receive an action potential from the controlling neuron.
When a few myofibers are stimulated, less force is produced. When all myofibers are stimulated, more force is produced. Increasing the frequency of action potentials also increases force.
Muscle contraction is described by the sliding filament model of contraction.
The actin and myosin filaments in muscle slide past each other, resulting in muscle contraction and the production of force.
The amount of force produced depends on the number of muscle fibers contracting.